Metallic treatment of polyphenyl thioethers to improve oxidative stability

ABSTRACT

A PROCESS WHICH COMPRISES CONTACTING POLYHENYL THIOETHERS WITH A METAL SELECTED FROM THE GROUP CONSISTING OF GROUP IB AND IIB OF THE PERIODIC TABLE THEREBY IMPROVING THE OXIDATIVE STABILITY OF SUCH THIOETHERS AND DECREASING THEIR CORROSIVENESS METALS. FOR EXAMPLE, M-BIS (PHENYLMERCAPTO) BENZENE IS MIXED WITH COPPER POWDER AND HEATED TO IMPROVE ITS OXIDATIVE STABILITY.

*United States Patent US. Cl. 260609 E Claims ABSTRACT OF THE DISCLOSURE A process which comprises contacting polyphenyl thioethers with a metal selected from the group consisting of Group Ib and 11b of the periodic table thereby improving the oxidative stability of such thioethers and decreasing their corrosiveness metals. For example, m-bis (phenylmercapto)benzene is mixed with copper powder and heated to improve its oxidative stability.

This application is a continuation of applicants copending application Ser. No. 512,212, filed Dec. 7, 1965, now abandoned.

This invention relates to the treatment of certain polyphenyl thioethers which can be classed as polyphenyl sulfides, which term is meant to include polyphenyl sulfides in which one or more, but not all, of the sulfur atoms have oxidative stability and to decrease their corrosiveness to metals.

Because of the wide variety of applications under which functional fluids are utilized, a concurrence of many properties, both physical and chemical, are needed in a particular fluid to provide the service demanded. One of the most rigorous demands on fluids is made by jet aircraft hydraulic systems and jet engine lubrication systems. As the speed and altitude of operation of jet powered aircraft increases, lubrication problems also increase because of higher operating temperatures and higher bearing pressures. resulting from the increased thrust needed to obtain higher speeds and altitudes. As the service conditions encountered become increasingly severe, the useful life of the functional fluid is, of course, shortened.

The useful life of any lubricant or hydraulic fluid can be adjudged on the basis of many criteria such as the extent of viscosity increase, the extent of corrosion to metal surfaces in contact with the lubricant and the extent of engine deposits. Those skilled in the art have found various ways to improve lubricants and to thus retard or prevent the eflfects which shorten the useful life of a lubricant. Thus, for example, small amounts of other materials, or additives, can be added to lubricants in order to affect one or more of the properties of the base lubricant. Oftentimes, however, it is difficult, especially as operating temperatures are increased, to find additives which will still perform the function for which they are added and yet not inject other problems.

Polyphenyl thioethers have been proposed as compounds which can be employed as functional fluids in many different types of application, such as hydraulic fluids, synthetic lubricants and atomic reactor coolants.

It has now been found that the oxidative stability and thus the useful life of polyphenyl thioethers can be greatly extended, even under the severe conditions encountered in jet engines and other devices operating at temperatures of the order of 600 F. and higher, by contacting such thioethers with metals of Groups Ib and 11b of the Periodic Table of Elements as shown in Handbook of Chemistry and Physics, published by the Chemical Rubber Publishing Company, 42nd edition, pp. 448 and 449. Also, by the process of this invention, significant improvements in the color and odor of such thioethers are realized, their corrosiveness toward ceutain metals is significantly reduced and there is an improvement in their electrical properties.

It is, therefore, an object of this invention to provide a method for increasing the oxidation resistance of polyphenyl thioethers and compositions thereof. Another object is to provide polyphenyl thioethers and compositions thereof which have decreased metal attack and give decreased formation of engine deposits. Still another object of this invention is to provide a process to improve the color and odor of polyphenyl thioethers.

As used herein the term polyphenyl thioether means a compound or physical mixture of compounds represented by the structures where m is a whole number from 0 to 6,

fl st j a-g I Where A and A are each selected from oxygen and sulfur,

@ flfli where x and y are whole numbers from 0 to 3 and the sum of x-l-y is from 1 to 6 and A and A are each selected from oxygen and sulfur but at least on of A and A is sulfur, and

where R R R and R are each selected from the group consisting of alkyl, alkoxy, haloalkyl, said alkyl and alkoxy radicals having from 1 to 4 carbon atoms, hydroxyl, aryl radicals, aryloxy radicals, phenylmercapto radicals, haloaryl radicals, alkaryl radicals, hydrogen and halogen, A, A and A are each selected from the group consisting of oxygen and sulfur provided at least one of A, A and A" is sulfur, in and n are integers from 0 to 3 provided the sum of m+n is at least 1, p is an integer from 1 to 3 and 0 is an integer from 0 to 1 providing at least one 0 is 1 and mixtures of the foregoing compounds.

Examples of such polyphenyl thioethers are:

Z-phenylmercapto-4'-phenoxydiphenyl sulfide 3-phenoxy-4-phenylmercaptodiphenyl sulfide 2-phenoxy-4-phenylmercaptodiphenyl sulfide 4-phenoxy-4-phenylmercaptodiphenyl sulfide 2-phenoxy-2'-phenylmercaptodiphenyl sulfide o-bis (phenylmercapto) benzene p-bis(phenylmercapto)benzene phenylmercaptodiphenyl bis phenylmercapto )biphenyl phenylmercapto (phenoxy) biphenyl bis(o-phenylmercaptophenyl) sulfide bis(p-phenylmercaptophenyl) sulfide bis(m-phenylmercaptophenyl) sulfide 1,2,3-tris (phenylmercapto benzene 1-phenylmercapto-2,3-bis(phenoxy)benzene l,2,4-tris(phenylmercapto) benzene 1,3,5-tris (phenylmercapto) benzene o-bis (o-phenylmercaptophenylmercapto)benzene p-bis(p-phenylmercaptophenylmercapto)benzene p-bis(o-phenylmercaptophenylmercapto)benzene p-bis(m-phenylmercaptophenylmercapto)benzene m-bis (p-phenylmercaptophenylmercapto)benzene o-bis (p-phenylmercaptophenylmercapto benzene ar-bis (phenylmercapto )-ar'- (phenylmercapto benzene 2,2-bis (phenylmercapto diphenyl ether 2.,3'-bis(phenylmercapto)diphenyl ether 2,4'-bis(phenylmercapto)diphenyl ether 4,4-bis (m-tolylmercapto) diphenyl ether 3,3-bis(m-toly1mercapto)diphenyl ether 2,4'-bis (m-tolylmercapto)diphenyl ether 3,4'-bis(m-tolylmercapto) diphenyl ether 3,3-bis(p-tolylmercapto)diphenyl ether 3,3'-bis(xylylmercapto)diphenyl ether 4,4-bis (xylylmercapto diphenyl ether 3,4'-bis (xylylmercapto)diphenyl ether 3,4'-bis(m-isopropylphenylmercapto)diphenyl ether 3,3-bis (m-isopropylphenylmercapto diphenyl ether 2,4-bis(m-isopropylphenylmercapto) diphenyl ether 3,4-bis p-tert.-butylphenylmercapto)diphenyl ether 4,4-bis (p-tert.-butylphenylmercapto)diphenyl ether 3,3-bis(p-tert.-butylphenylmercapto)diphenyl ether 3,3-bis(m-di-tert.-butylphenylmercapto)diphenyl ether 3 ,3 '-bis(m-chlorophenylmercapto diphenyl ether 4,4-bis (m-chlorophenylmercapto diphenyl ether 3 3 '-bis m-trifluoromethylphenylmercapto diphenyl ether 4,4'-bis m-trifluoromethylphenylmercapto diphenyl ether 3 ,4'-bis (m-trifluoromethylphenylmercapto diphenyl ether 2,3 -bis m-trifluoromethylphenylmercapto diphenyl ether 3,3 -bis (p-trifluoromethylphenylmercapto diphenyl ether 3 3 '-bis o-trifiuoromethylphenylmercapto diphenyl ether 3,3'-bis(m-methoxyphenylmercapto) diphenyl ether 3,4'-bis (m-isopropoxyphenylmercapto)diphenyl ether 3 ,4'-bis m-p erfluorobutylphenylmercapto) diphenyl ether Z-m-tolyloxy- -phenylmercaptodiphenyl sulfide 2-p-tolyloxy-3-phenylmercaptodiphenyl sulfide 2-o-tolyloxy-4'-phenylmercaptodiphenyl sulfide 3-m-tolyloxy-3-phenylmercaptodiphenyl sulfide 3-m-tolyloxy-4'-phenylmercaptodiphenyl sulfide 4-m-tolyloxy-4'-phenylmercaptodiphenyl sulfide 3-xylyloxy-4'-phenyhnercaptodiphenyl sulfide 3-xylyloxy-3'-phenylmercaptodiphenyl sulfide 3-phenoxy- '-m-tolylmercaptodiphenyl sulfide 3-phenoxy-4-m-tolylmercaptodiphenyl sulfide 2-phenoxy-3'-p-tolylmercaptodiphenyl sulfide 3-phenoxy-4'-m-isopropylphenylmercaptodiphenyl sulfide 3-phenoxy-3'-m-isopropylphenylmercaptodiphenyl sulfide 3-m-tolyloxy-3 -m-isopropylphenylmercap todiphenyl sulfide 4-m-trifiuoromethylphenoxy- '-phenylmercaptodiphenyl sulfide 3-m-trifiuoromethylphenoxy-4-phenylmercaptodiphenyl sulfide 4 Z-m-trifluoromethylphenoxy- -phenylmercaptodiphenyl sulfide 3-m-trifiuoromethylphenoxy-3-phenylmercaptodiphenyl sulfide 3-p-chlorophenoxy-3'-phenylmercaptodiphenyl sulfide and 3-m-bromophenoxy-4'-phenylmercaptodiphenyl sulfide.

Mixtures of polyphenyl thioethers can be treated according to the method of this invention. A typical mixture of polyphenyl thioethers is one which contains by weight from about 45% to about 55% m-phenoxyphenyl m-phenylmercaptophenyl sulfide, from about 25% to about 35% bis(m phenylmercaptophenyl)sulfide and from about 18% to about 25% bis(m-phenoxyphenyl) sulfide.

The term metal as used herein is intended to include the elemental and oxide form thereof. Most metals of Groups Ib and III) are commercially available in many forms such as wire, sheet and granules, any of which can be used in the process of this invention. The preferred metals are copper, zinc and silver.

In carrying out the process of this invention, the contacting of the fluid with the metal can be etfected by means known to the art for contacting solids and liquids, e.g., by agitating a mixture of the fluid and the metal or by passing the fluid through a packed column of the metal. The fluid can be recovered after treatment by means known to the art for separating liquids from solids as by filtration or by distilling the liquid from the treatment vessel under reduced pressure.

Generally the improvements in the fluid properties obtained by the process of this invention are unaffected by the concentration of the metal, the time of contact or the temperature; however, it should be realized that there are minimum values of concentration, time and temperature below which the process of this invention becomes impractical. A minimum concentration of metal. of about 0.1% by weight of polyphenyl thioether to be treated should be used.

On the other hand, the benefits obtained are afifected by particle size. The extent of the benefit obtained appears to increase as the particle size of themetal or oxide decreases. Thus, contacting such a fluid as above described with copper wire increases oxidative stability of the fluid; however, under similar conditions copper powder increases to a much greater degree the oxidative stability of the fluid. The length of time of contact will vary depending upon variances in the particle size but a minimum time of about one hour at about 25 C. should be used. In general, times in the order of 1 to 48 hours are suflicient for most conditions.

The temperature at which the process of this invention is carried out can vary from about 25 C. to 350 C. or higher. The choice of a particular temperature will be dictated, for example, by time available, by the facilities available, particle size of the metal and the characteristics of the fluid being treated. For example, when using the metal in powder form, a contact period of from about 8 to about 16 hours at temperatures in the range of about 200 C. to about 300 C. provide the optimum efiiciency of equipment and benefit to the fluid.

The mechanism through which the improvements in the properties of the ethers treated according to the method of this invention occurs is not completely understood at this time. However, such improvements are wholly unexpected in view of the lack of purifying capability known or attributed to such metals or their oxides such as an adsorption mechanism. Particularly unexpected are the improvements in the color and odor of the above-described fluids brought about by the process of this invention.

Of the metals in Groups Ib and 11b of the Periodic Table of Elements, copper is most preferred in the process of this invention because of its low cost and general availability in many forms. More particularly copper powder in a form generally termed electrolytic dust has.- been found to be best suited for the process of this invention.

The following non-limiting examples illustrate the process of this invention.

EXAMPLE 1 Into a suitable boiling flask equipped with temperature sensing means, a distillation column and means for agitating the contents there was charged 35.18 grams of m-bis(phenylmercapto)benzene having a decomposition temperature of 635 F. and .70 gram of copper powder commonly termed electrolytic dust (ED). The mixture was heated in the range of 230 C. to 260 C. and held in that temperature range for 16 hours during which time the mixture was agitated. The thus treated fluid had very little odor as compared to the untreated fluid and had a comparatively lighter color. The decomposition temperature of the treated fluid was 707 F.

Separate samples of m-bis(phenylmercapto)benzene, hereinafter designated as fluid A, were treated by contacting them with other metals of this invention in the manner of Example 1. Also, in similar manner, a fluid, hereinafter designated fluid B, consisting by weight of 22% bis- (m-phenoxyphenyl)sulfide, 30% bis(m-phenylme1'captophenyl)sulfide and 48% m-phenoxyphenyl m-phenylmercaptophenyl sulfide was treated by contacting separate samples with copper and copper oxides. The results of the treatments are reported below in Table I. In each case results similar to that stated in Example 1 were obtained with regard to color, odor and decomposition temperature.

The data reported in Table I was obtained employing one of the major bench scale methods used for evaluating the oxidative stability of a lubricant. The procedure is described in Federal Test Specification 791, Method 5308, excepting that the fluid to be tested is heated to a temperature of 500 F. for a period of 48 hours instead of 250 F. for 168 hours in the presence of certain metals and oxygen and the viscosity increase of the lubricant is determined. Additionally, information as to the corrosiveness of a lubricant to metals can also be obtained. In order to demonstrate the effectiveness of the process of this invention in improving the oxidative stability and reduced corrosiveness of the fluids, samples of the fluid treated as in the above example and untreated samples of the same fluids were tested. The metal specimens used were steel, copper, silver, titanium, magnesium alloy and aluminum alloy. However, only the results upon copper and silver are reported since the untreated compositions tested had essentially no effect no steel, magnesium alloy, titanium and aluminum alloy. Viscosity measurements were made according to ASTM Method D-445-53T using a Cannon-Fenske modified Ostwald viscosimeter. The percent viscosity increase was determined by measuring the viscosity of the samples before and after the test, dividing the difference by the original viscosity and multiplying the quotient by 100. The corrosiveness to metals was determined by Weighing metal specimens of known size before and after the test.

TABLE I.EFFEOT OF METAL TREATMENT Percent viscosity Metal attack,

increase mg. /c1:n.

Control Cuprous oxide- Cupric oxide It has been found that the method of this invention can be employed in series combination with other treatments of the functional fluids herein described. For example, the

oxidative stability of polyphenyl thioethers can be improved by contacting such fluids with alumina. The term alumina or activated alumina is used herein in its normal sense and thus means a porous form of aluminum oxide of high surface area generally prepared by thermally treating hydrated alumina. The following example demonstrates the effect of such series combination treatments.

EXAMPLE 9 Two portions of fluid A, one contacted with zinc dust and one contacted with silver filings in the manner of Example 1, were treated with activated alumina as follows. A four-inch by eighteen-inch glass column, containing, from the bottom, a one-quarter inch layer of filter aid and a ten-inch layer of activated alumina, was fitted to a receiving vessel capable of sustaining subatmospheric pressure. Each sample of fluid A at about 50 C.-60 C. was passed through the column while maintaining a vacuum in the receiving vessel. After such treatment the samples were subjected to oxidation and corrosion tests as explained above. The results of such tests appear in Table II below. While it is preferred to perform the treatments in the order shown in the above example, alternatively the two treatments may be performed in reverse order, i.e., contact the fluid first with alumina and thereafter contact the fluid with a metal of Groups Ib and III] of the Periodic Table of Elements.

TABLE II.EFFEOT OF SERIES TREATMENT Percent viscosity increase Occasionally it has been found necessary to promote desirable characteristics of a fluid or to suppress undesirable characteristics by incorporating therein minor amounts of additives. Some of these additives while performing their intended function often tend to cause increased sludge deposit when the fluid containing them is subjected to high temperature in the order of 500 F. to 600 F. The process of this invention is beneficial in reducing the tendency of the polyphenyl thioether containing such additives to deposit sludge when subjected to high temperatures.

While this invention has been described with respect to various specific examples and embodiments, it is understood that the invention is not limited to such examples and embodiments and that it can be variously practiced within the scope of the following claims.

What is claimed is:

1. The process for improving the oxidative stability of polyphenyl thioethers which comprises forming a mixture of a polyphenyl thioether and a metal of the class consisting of copper, Zinc, silver or the oxides thereof, wherein said metal or oxide thereof is present in amounts of at least about 0.1% by weight of the polyphenyl thioether, and maintaining said mixture at a temperature of from 25 C. to 350 C. for a time sufficient to improve the oxidative stability.

2. The process as in claim 1 wherein the polyphenyl thioether is mixed with copper.

3. The process as in claim 1 wherein the polyphenyl thioether is contacted with alumina prior to or after being mixed with the metal or oxide thereof.

4. The process as in claim 1 wherein the polyphenyl thioether is a composition comprising by weight of from about 45% to about 55% m-phenoxyphenyl m-phenylmercaptophenyl sulfide, from about 25% to about 35% bis (m-phenylmercaptophenyl)sulfide and from about 18% to about 25 bis (m-phenoxyphenyl)sulfide.

5. The process as in claim 1 wherein the polyphenyl thioether is a mixture comprising by weight about 48% m-phenoxyphenyl m-phenylmercaptophenyl sulfide, about 30% bis (m-phenylmercaptophenyl)sulfide and about 22% bis m-phenoxyphenyl sulfide.

6. The process as in claim 1 wherein the polyphenyl thioether is m-bis(phenylmercapto)benzene.

7. The process as in claim 1 wherein the polyphenyl thioether is a mixture by weight 48% m-phenoxyphenyl m-phenylmercaptophenyl sulfide, about 30% bis(mphenylmercaptophenyl) sulfide and about 22% bis-(mphenoxyphenyl)sulfide and the metal oxide is cuprous oxide.

8. The process as in claim 6 wherein the metal is copper.

9. The process as in claim 6 wherein the metal is silver. 10. The process as in claim 6 wherein the metal is zinc.

References Cited UNITED STATES PATENTS 3,119,877 1/1964 Campbell et a1 260609 CHARLES B. PARKER, Primary Examiner 10 D. R. PHILLIPS, Assistant Examiner US. Cl. X.R. 

